Capsular products

ABSTRACT

Microscopic capsules comprising a nucleus surrounded by a film-forming polymeric layer having a substantially continuous light-reflecting metallic coating thereover.

This application is a division of my copending U.S. application Ser. No.545,333, filed Apr. 26, 1966, now U.S. Pat. No. 3,468,662 which, inturn, is a continuation-in-part of U.S. application Ser. No. 108,774,filed May 9, 1961 and now U.S. Pat. No. 3,276,869, issued Oct. 4, 1966.

This invention relates to capsules adapted to retain solid and fluidmaterials and to the use of such capsules in photographic colorprocesses for forming monochromatic and multichromatic images and tophotographic products for carrying out said processes.

A principal object of the present invention is to provide improvedcapsules, that is, improved capsules of the construction comprising anucleus of a solid or fluid material contained or encapsulated within ashell-like coating of a film-forming polymeric material, the outermostsurface or wall of the capsules being coated with a suitable material topredeterminedly modify said wall.

Another object of the invention is to provide minute capsules of theaforementioned construction which possess substantially highimpermeability or imperviousness to prevent loss of encapsulated fluidmaterial or to occlude environmental substances such as water vapor oroxygen or the like from contact with encapsulated material which may besensitive or reactive therewith.

Still another object of the present invention is to provide color imagesby a process wherein the effective emulsion speed of the photosensitiveelement employed is substantially increased by utilizing minute capsulesof the aforementioned construction.

Another object of the invention is to provide novel products andprocesses utilizing minute capsules of the aforementioned constructionfor forming color images by transfer techniques wherein an imagewisedistribution of one or more color-providing substances is formed inunexposed parts of a negative photosensitive element having one or morelight-sensitive portions having silver halide therein and transferred toan image-receiving element, and wherein the imagewise distribution ofeach color-providing providing substance so transferred by imbibitionand deposited upon the image-receiving element arranged in superposedrelation to the negative photosensitive element colors theimage-receiving element a predetermined color to provide therein amonochromatic or multichromatic image comprising one or more positiveimages of negative latent color images formed by the exposure of saidphotosensitive element.

Still another object of the invention is the provision of aphotosensitive element, usable in a color process which comprises asupport, one or more light-sensitive portions comprising a silver halideemulsion, capsules containing at least a predetermined color-providingsubstance, such as, for example, a dye which is capable of coupling withan oxidized silver halide developer or a dye which is itself a silverhalide developer, associated with each light-sensitive portion, thecolor-providing substance employed adapted to be transferred at least inpart to an image-receiving element for coloring said image-receivingelement, said capsules having a light reflecting coating for increasingthe effective emulsion speed of the photosensitive element.

A further object of the invention resides in the provision of aphotographic product in the nature of a film unit especially adapted foruse in a transfer process and comprising a photosensitive element ornegative material of the character described above, a positiveimage-receiving element adapted to be associated with said negativephotosensitive element in superposed relation thereto, and a containerholding a liquid processing composition for processing said film unitafter exposure thereof.

A further object of the present invention is to provide novelphotographic processes and products for obtaining color images bydiffusion-transfer processes, wherein color-providing substances such asdye developers utilized to provide said colored images are encapsulatedwithin minute capsules of alkali-permeable polymeric material, saidcapsules being coated with silver halide.

Still another object of the present invention is to provide novelphotosensitive elements comprising at least one layer containing minutecapsules of alkali-permeable polymeric material, said capsulescontaining therewithin a color-providing substance and being coated withsilver halide.

Still another object of the present invention is to provide novel minutecapsules of alkali-permeable polymeric material containing therewithin acolor-providing substance, said capsules being coated with silverhalide.

Other objects of the invention will in part be obvious and will in partappear hereinafter.

The invention accordingly comprises the several steps and the relationand order of one or more of such steps with respect to each of theothers, and the products possessing the features, properties and therelation of elements which are exemplified in the following detaileddisclosure and the scope of the application of which will be indicatedin the claims.

For a fuller understanding of the nature and objects of the invention,reference should be had to the following detailed description taken inconnection with the drawings wherein:

FIG. 1 is a broken-away, side elevation of an apparatus for performingsteps of a process for producing products of the present invention;

FIG. 2 is a cross-section of the apparatus of FIG. 1, takensubstantially above the line 2--2;

FIG. 3 is a diagrammatic enlarged side elevation of one embodiment of afilm unit comprising a negative photosensitive element useful incarrying out the practices of this invention and, in association withsaid photosensitive element, an image-receiving element and a rupturablecontainer, the three elements together providing a photographic productemployable to carry out a photographic transfer process;

FIG. 4 is a diagrammatic enlarged sectional view illustrating theassociation of elements during one stage of the performance of atransfer process, the thickness of the various materials beingexaggerated, and FIG. 4 further illustrates another embodiment of aphotosensitive element useful in carrying out the practices of theinvention for the formation of multicolor images;

FIG. 5 is a diagrammatic enlarged sectional view of still anotherembodiment of a photosensitive element useful in carrying out thepractices of this invention;

FIG. 6 is a diagrammatic enlarged sectional view of still anotherembodiment of a photosensitive element useful in carrying out thepractices of this invention;

FIG. 7 is a diagrammatic cross-sectional view of a photographic filmunit for use in obtaining monochromatic images, and comprising aphotosensitive element, an image-receiving element and a rupturablecontainer holding a liquid processing fluid;

FIG. 8 is a diagrammatic cross-sectional view of one embodiment of thisinvention for use in obtaining multicolor images, during processing, andcomprising an integral multilayer photosensitive element, animage-receiving element and a processing fluid;

FIG. 9 is a diagrammatic cross-sectional view of another embodiment ofthis invention for use in obtaining multicolor images, duringprocessing, and comprising a photosensitive element, an image-receivingelement and a processing fluid; and

FIG. 10 is a diagrammatic cross-sectional view of still anotherembodiment of this invention for use in obtaining multicolor images,during processing, and comprising a photosensitive color screen element,an image-receiving element and a processing fluid.

The formation in a variety of sizes and shapes of capsules consisting ofa nucleus comprising, for example, a liquid around which is deposited adense shell-like coating of a film-forming organic polymeric material iswell known to the art. A great number of materials in solid or liquidform may be encapsulated. For example, materials such as mineral andvegetable oils, kerosene, gasoline, turpentine, carbon tetrachloride,chloroform, flavors, perfumes, catalysts, propellants, oxidizers,medicines, e.g., vitamins, color-providing substances or materials,e.g., dye developers, adhesives, magnetic materials and a host of othershave been encapsulated. Release of the encapsulated material at therequired time may be accomplished in any one of several ways such as,for example, rupturing or breaking, melting, dissolving, etc. thecapsule wall.

The applications or uses for such encapsulated materials are obviouslynumerous. For example, in U.S. Pat. Nos. 2,712,507, 2,730,456 and2,730,457 there is disclosed, for use in manifold record materials,microscopic pressure-rupturable capsules comprising film-forminghydrophilic colloid material deposited around a central nucleus of anoily water-immiscible printing fluid. In U.S. Pat. No. 2,932,582 thereis disclosed a transfer record sheet having a coating of microscopic,pressure-rupturable capsules containing a liquid solvent or vehicle fora coloring material carried by said sheet in solid form. In U.S. Pat.No. 2,907,682, there is disclosed adhesive tapes which employmicroscopic pressure-rupturable capsules containing solid solubleadhesive and microscopic pressure-rupturable capsules containing aliquid solvent for the solid adhesive used. The use of encapsulated dyeshas also been proposed for various photographic systems.Pressure-rupturable capsules containing particles of magnetic material,e.g., magnetic iron oxide, have been disclosed for printing purposes.Other uses are as means for storing and handling hazardous, reactive,toxic or noxious materials, etc.

In a great many uses, a capsule wall of high impermeability is desiredin order, for example, to prevent loss of encapsulated fluid material orto exclude environmental substances such as moisture, oxygen or the likefrom contact with the encapsulated material. In the present inventionthere are provided capsules having the outer surfaces or walls thereofcoated with a thin continuous film or layer of a metal such as, forexample, aluminum or other material, for example, polymericfluorocarbons which increase the impermeability of the capsule wallwithout at the same time (a) appreciably increasing the wall thicknessor capsule size, (b) appreciably modifying the rupture or releasecharacteristics of the capsule wall, and (c) undesirably modifying thewall-to-fill ratio. The thin continuous coating may be applied to anyone of several methods such as, for example, spraying, electroplating,vapor deposition and the like.

The minute capsules of the present invention may be formed offilm-forming polymeric material of a hydrophilic nature or charactersuch as, for example, gelatin; or they may be formed of film-formingpolymeric material of a hydrophobic nature such as, for example,polyvinyl chloride. Each capsule consists of a nucleus comprising, forexample, a solid or substantially solid material, e.g., magnetic ironoxide or a fluid material, e.g., a color-providing substance in solutionor dispersed in a suitable medium around which has been deposited adense shell-like coating of film-forming polymeric material which may bepressure-rupturable.

The encapsulating material which encloses or surrounds the nucleus maycomprise one or more hydrophilic film-forming polymeric materials or oneor more film-forming hydrophobic polymeric materials. Thus, hydrophilicpolymeric materials such as gelatin, gum arabic, methyl cellulose,starch, alginates, polyvinyl alcohol, casein, agar-agar and the like maybe utilized as encapsulating materials. It is also possible to employ asthe encapsulating material a "complex" of film-forming hydrophilicpolymeric materials. By a "complex" of hydrophilic polymeric materialsis meant the product resulting from the union in a suitable medium oftwo kinds of hydrophilic polymeric materials having opposite ioniccharges in said medium, the union being brought about by such differencein charge. Hydrophobic polymeric materials such as, for example,polyvinyl chloride, butadiene-styrene containing resins, acrylic resins,urethanes, fluorocarbons, polyethylene, polyvinylidine chloride,regenerated cellulose and the like, may also be employed as therelatively thick or self-supporting shell-like encapsulating wall. Theencapsulating material selected in any specific instance depends uponthe encapsulating process employed and the particular material to beencased therewithin.

There are many ways in which the capsules of the present invention maybe formed and which are well known to the art. Suitable methods aredescribed, for example, in U.S. Pat. Nos. 2,800,457, 2,800,458, and2,907,682. One illustrative method of making minute or microscopiccapsules of film-forming hydrophilic polymeric material containing acolor-providing substance such as a dye or dye intermediate comprisesmaking an aqueous sol of a hydrophilic polymeric material, e.g.,gelatin, and emulsifying therein a water-immiscible organic liquid, inwhich the color-providing substance is dissolved or stability suspendeduntil the required microscopic drop size is attained, and thereafterdiluting the emulsion with water or an acidified aqueous solution insuch amount so as to cause the hydrophilic polymeric material to depositaround each microscopic drop of adhesive. All of the foregoing steps arecarried out at a temperature above the gelatin or solidification pointof the polymeric material. In the case of gelatin, the temperatureduring these steps is maintained at 50° C. or above. Gelation orsolidification of the encapsulating material is then achieved by coolingto a temperature below the gelation or solidification point of thematerial. If this latter step is performed rapidly, as by rapid cooling,the pore size of the resultant capsules will be small. If the gelationstep is performed slowly, the pore structure of the encapsulatingmaterial will be coarser. At this point the encapsulation of thecolor-providing substance with hydrophilic polymeric material iscomplete.

If it is desirable to make the capsular material, as produced above,hard, more heat resistant and insoluble in water, it can be treated, forexample, with a well-known gelatin hardener, e.g., formaldehyde and thelike. If desired, after hardening and drying, the agglomerate mass ofcapsules may be comminuted to form fine granules of any desired size.

An illustrative method of making capsules of two hydrophilic polymericmaterials such as gelatin and gum arabic comprises forming twocompatible sols by dispersing hydrophilic materials such as gum arabicand gelatin in water, mixing the two aqueous sols together and thenemulsifying therein the water-immiscible organic liquid andcolor-providing substance or emulsifying the organic liquid andcolor-providing substance in one of the sols first and then mixing theemulsion with the second sol. The pH of the emulsion so formed, ifnecessary, may be adjusted so that the ions of the two materials, e.g.,gum arabic and gelatin have different electric charge. Deposition of acomplex of hydrophilic materials around microscopic nuclei or dropletsof the water-immiscible organic liquid containing a color-providingsubstance is achieved by dilution with water and/or changing the pH ofthe mixture. All of the foregoing steps are carried out at temperaturesabove the gelation or solidification point of the hydrophilic polymericmaterial. Gelatin is achieved as previously described, that is, bycooling the complex encapsulating material below its gelatin orsolidification temperature.

More detailed descriptions of preparing minute capsules by emulsiontechniques as illustrated above may be found in a number of patents. Forexample, U.S. Pat. Nos. 2,800,457 and 2,800,458 disclose mixtures formaking minute oil-containing capsules. The droplet of enclosed oil mayhave suspended or dissolved therein a dye or dye intermediate. U.S. Pat.No. 2,907,682 discloses methods for encapsulating adhesive materials aswell as methods for encapsulating solvents or vehicles for said adhesivematerials. U.S. Pat. No. 2,932,582 discloses methods for encapsulatingliquid solvents or vehicles for printing or marking materials. U.S. Pat.No. 2,953,454 discloses a method for encapsulating a color-formingmaterial whose electromagnetic absorption characteristics may bereversibly changed by different applied electromagnetic radiations. U.S.Pat. No. 2,971,916 discloses a method for making capsules containing amagnetic material. The encapsulation of other materials has also beendisclosed in a number of the above patents.

Another encapsulation method known to the art comprises feeding orextruding a film-forming encapsulating material in viscous liquid forminto a nozzle where it forms a membrane over the nozzle's orifice andintroducing into such membrane through a tube leading to the orifice afiller material, e.g., color-providing substance. In one embodiment thefilm-surrounded filler separates into minute capsules by gravitationaland surface tension forces. In another embodiment the film-surroundedfiller is ejected from the nozzle by centrifugal force. In each case theminute capsules so formed are dropped or flung into a suitable bath tocause hardening or setting of the encapsulating film-forming material.More detailed descriptions of making capsules according to the abovetechniques may be found, for example, in U.S. Pat. No. 2,275,154,Chemical and Engineering News, July 13, 1959, page 44, and Design News,June 20, 1960.

The permeability of fluids through the capsule walls may be decreased byproviding the outer wall or surface of the capsules with a thincontinuous coating of suitable material, preferably a metal such as, forexample, aluminum. One process for coating each capsule with a thincontinuous film or layer of a metal or metal-bearing compound, e.g.,metal oxide, or other material, e.g., Teflon (Trademark of E. I. du Pontfor tetrafluoroethylene polymers), involves vacuum deposition. The stepof vacuum depositing may involve either thermally evaporating or cathodesputtering at pressures below about 100 microns of mercury and usuallywithin the range of from 0.1 to 100 microns of mercury and depositingthe vaporized material as a thin continuous coating upon the outer wallof the capsules. When the vacuum deposition is effected by thermalevaporation, pressures below 10 microns are usually employed. Thetemperature employed, in any case, is dependent upon the material beingevaporated and pressure. When the vacuum deposition is effected bycathode sputtering, voltages of the order of 5 to 10 kilowatts, andpressures of from 10 to 20 microns of mercury are common.

Among the large number of metals or metallic materials capable of beingvacuum deposited upon the outermost surfaces of capsules, mention may bemade of, for example, aluminum, silver, zinc, magnesium, cadmium,chromium, cobalt, copper, gold, nickel, iron, tin, platinum, palladiumand the like. Metal oxides such as aluminum oxide, tin oxide and othermetal-containing compounds may also be employed as the capsule coating.Organic materials such as certain polymeric materials, e.g., Teflon, mayalso be vacuum deposited upon the capsules. The thickness of thevacuum-deposited coating may be varied or controlled, suitablethicknesses generally being within the range of 0.1 to 1 micron. Thickercoatings, for example, between 1 and 10 microns may be depositedespecially when maximum impermeability is desired. It should be pointedout that the capsule wall coating may comprise one or more materials.For instance, the coating may comprise a single metal or an alloy or itmay comprise two or more distinct layers of different metals such as,for example, a first layer comprising copper and a second layerovercoated on said first layer comprising aluminum.

FIGS. 1 and 2 illustrate an apparatus for evaporating a material 20 ontocapsules 22. Material 20, for example, is a metal in the form of acoating upon a wire gauze. Capsules 22 are contained within acylindrical glass jar 24, one end of which is closed at 26 and the otherend of which is provided with an open mouth 28. Gauze 20 is supported bya mounting arm 30 extending through mouth 28 and carried by a standared32. Jar 24 rests upon a pair of rollers 34 and 36, the ends of which arejournaled in bearing mounts 38 and 40. A motor 42 is provided forrotating rollers 34 and 36 through gearing 37 in order to cause rotationof jar 24, which is prevented from moving longitudinally by circularflanges 44 at the ends of the rollers. As shown, electrical leads 46 and48 are connected to the opposite extremities of gauze 20 in order totransmit a suitable electric current through the gauze from a powersupply (not shown). In operation, a sufficient current is transmitted byleads 46 and 48 through gauze 20 for generating sufficient heat to causerapid evaporation of the coating of gauze 20. At the same time, motor 42causes rotation of rollers 34 and 36 so that capsules 22 arecontinuously agitated by movement of the inner surfaces of jar 24 aswell as a plurality of ribs 50 projecting inwardly from the innersurfaces of the jar. The apparatus, including jar 24, is mounted on abase plate 52 and enclosed by such means as a glass cylinder 54 and acover plate 56. O-ring gaskets 57 hermetically seal glass cylinder 54between base plate 52 and cover plate 56. A pump (not shown)continuously exhausts the region defined by base plate 52, glasscylinder 54 and cover plate 56 through a conduit 60. Capsules 22, as aresult, become coated with a thin continuous coating of the metal whichinitially was part of gauze 20.

Instead of employing a metal coated wire gauze, there may be employedone or more metal-containing crucibles suitably heated such as byresistance or induction. The crucible may be composed of carbon ortantalum or some other material or materials well-known to the art.

Another method for producing a thin continuous metallic coating oncapsule walls involves so-called "cathode sputtering". When anelectrical discharge is passed between electrodes under low gaspressure, the cathode electrode is slowly disintegrated underbombardment by ionized gas molecules. The disintegrated material leavesthe cathode surface and is condensed on capsules provided around thecathode. Likewise, other apparatus for carrying out the process whereinthe capsules are moved past a source of vacuum evaporated metal whilebeing held in a circumferential path by centrifugal force isillustrated, for example, in U.S. Pat. No. 2,846,971. In addition toapparatus of the above-mentioned type, there may also be employedapparatus wherein the capsules are coated by allowing them to freelyfall through vapors of the metal provided by one or more sources. Onesuch apparatus is illustrated, for exaple, in U.s. Pat. No. 2,374,331.

Another process for coating each capsule with a thin continuous metallicfilm or layer involves plating techniques such as electroplating. Sincethe capsule walls are non-metallic, the outer surface must be madeconductive before plating. This may be achieved by vacuum depositing avery thin coating of a conductive metal, e.g., copper, upon the outercapsule wall as described above or a shellac or lacquer with asuspension of a conductive material such as a conductive metal powder,e.g., bronze powder, or graphite can be sprayed or dusted on the outercapsule walls. Capsules provided with a conductive surface may be platedwith a continuous metallic coating of a suitable thickness, e.g., 0.1 to1 micron, by any one of the many appropriate electroplating techniqueswell known to the art.

It should be mentioned that the thin continuous capsule coating of ametal or other material in addition to imparting increasedimpermeability to the capsule wall may also serve some other purpose orrole such as, for example, for light reflectivity, for reaction with thenucleus material etc.

One particular applicability of the capsules of the present invention isin certain products or assemblages useful in photographic transferreversal processes capable of producing a color print. In processes forforming color images by transfer techniques, an imagewise distributionof one or more color-providing substances is formed in unexposed partsof a negative photosensitive element having one or more light-sensitiveportions having silver halide therein and transferred to animage-receiving element. The imagewise distribution of eachcolor-providing substance so transferred and deposited upon theimage-receiving element arranged in superposed relation to the negativephotosensitive element colors the image-receiving element apredetermined color to provide therein a monochromatic or multichromaticimage comprising one or more positive images of negative latent colorimages formed by the exposure of said photosensitive element. Among thetechniques for carrying out a transfer process in color, mention may bemade of, for example, (a) the processes disclosed and claimed in thecopending application of Howard G. Rogers, Ser. No. 748,421, filed July14, 1958, now U.S. Pat. No. 2,983,606 wherein dye developers (i.e.,compounds which contain in the same molecule both the chromophoricsystem of a dye and also a silver halide developing function) are thecolor-providing substances or color-forming components; (b) theprocesses disclosed in U.S. Pat. No. 2,774,668 and copendingapplications Ser. No. 565,135, filed Feb. 13, 1956, now U.S. Pat. No.3,345,163 Ser. No. 748,421, previously cited, now U.S. Pat. No.2,983,606, and Ser. No. 613,691, filed Oct. 3, 1956, now U.S. Pat. No.3,087,817 wherein complete dyes of suitable colors and of a naturehaving a coupling group or function and which are able to couple withsilver halide developers in oxidized condition are the color-providingsubstances; (c) the processes disclosed and claimed in U.S. Pat. Nos.2,647,049, 2,661,293, 2,698,244, 2,698,798 and 2,802,735 wherein colorcoupling techniques are utilized which comprise, at least in part,reacting one or more developing agents and one or more color formers toprovide a positive color image in a superposed image-receiving layer;and (d) the processes disclosed in the copending application of HowardG. Rogers, Ser. No. 825,359, filed July 6, 1959, now U.S. Pat. No.3,185,567 wherein the color-providing substances employed are initiallyimmobile or nondiffusible but which are rendered diffusible in unexposedareas of the photosensitive layer by reaction with unreacted orunexhausted silver halide developing agent. Such color-providingsubstances are hereinafter referred to as "reducible dyes".

The expression "color-providing substances" as used herein is intendedto include all types of reagents which may be utilized to produce acolor image, and such reagents may initially possess the desired colorof may undergo a reaction to give the desired color. In a preferredembodiment, the color-providing substances are dye developers, that is,complete dyes which have a silver halide developing function asdisclosed, for example, in the copending application of Howard G.Rogers, Ser. No. 748,421, now U.S. Pat. No. 2,983,606. The use of colorformers or couplers which react with the oxidation product of colordevelopers to produce a dye, and therefore dye intermediates, is alsocontemplated within the term "color-providing substance". The use ofcomplete dyes per se as color-forming substances is also within thescope of this invention. The nature of these and other color-providingsubstances will be referred to in more detail hereinafter.

It has been found that color-providing substances such as mentionedabove utilized to provide color images may be encapsulated or containedwithin a shell-like coating of a film-forming polymeric material. Thenucleus of such capsules may comprise a color-providing substance insubstantially solid form which is, for example, solubilized by theprocessing composition or the nucleus may comprise a suitable liquidsolvent or medium in which a color-providing substance is dissolved orsuspended. In order to prevent loss of the nucleus liquid and/or toretard or prevent undesirable environmental materials from reacting withthe nucleus materials, the outer surfaces of the capsule wall are coatedwith a thin continuous film such as, for example, of aluminum or silver.These capsules may be utilized in the photosensitive element, forexample, in or behind the silver halide emulsion. Preferably, a coatingor layer of the capsules containing a color-providing substance, e.g., adye developer, is placed behind the silver halide emulsion, i.e., on theside of the emulsion adapted to be located most distant from thephotographed subject when the emulsion is exposed and most distant fromthe image-receiving element when in superposed relationship therewith.Placing such capsule layer or stratum behind the emulsion has theadvantage of providing increased contrast in the positive image.

When employing a layer or stratum of capsules which contain, forexample, a dye developer, reducible dye or complete dye in the preferredmanner, i.e., behind the silver halide emulsion, it has been found thatthe effective emulsion speed can be substantially increased by havingthe outer surfaces or portions of such capsules provided with a thincoating such as of a suitable metal adapted to reflect light of allvisible wave lengths incident upon it. The increase in effectiveemulsion speed is apparently due to the fact that previously the coloreddye would ordinarily absorb light whereas now the reflecting coatingutilizes some of the otherwise wasted light to increase the absorptionof light in the emulsion when it is exposed. Thus the emulsion iseffectively more sensitive since the exposure depends on the absorptionof light.

In its broadest aspect, the emulsion speed of a photosensitive elementmay be increased by employing a light-reflecting environment, eitherdiffuse or specular reflecting, behind a silver halide emulsion, but infront of the color-providing substance. This broad concept isconveniently carried out by the employment of a photosensitive elementwhich comprises a support carrying thereon a photosensitive layer orstratum comprising a liquid-permeable material, for example, gelatin orother water- and alkali-permeable carrier having silver halide therein,and a layer comprising a profusion of minute capsules behind thephotosensitive layer, said capsules comprising a wall or shell-likecoating of a film-forming polymeric material surrounding a nucleuscontaining a predetermined color-providing substance such as, forexample, a dye developer, the outer surfaces of said capsules having asuitable light-reflecting coating. In the present invention there isthus employed capsules having the outer surfaces of the capsule wallcoated with a thin, light-reflecting film or layer such as, for example,of silver or aluminum which not only increases the effective emulsionspeed but also increases the impermeability of the capsule walls so asto prevent loss of encapsulated liquid material or to excludeenvironmental substances such as moisture, oxygen or the like fromcontact with the encapsulated materials. The minute capsules may beformed by processes such as previously mentioned. The thin continuouslight-reflecting coating may be applied to the capsule walls by any oneof several methods such as, for example, spraying, electroplating, vapordeposition and the like as heretofore described.

A further understanding of the inventive concepts herein may be gainedby reference to the drawings. For purposes of simplicity the drawingswill be described in connection with the use of dye developers, althoughother dyes such as reducible dyes, complete dyes and the like can alsobe employed in a like manner. One embodiment of a photographic film unitor assembly useful in carrying out a one-step photographic process forthe formation of an image of an individual color is illustrated in FIG.3. In FIG. 3 there is shown a film unit making use of a positive sheetmaterial or image-receiving element 70 comprising an image-receivinglayer of opaque or transparent material which is liquid-permeable anddyeable from alkaline solutions and which has been illustrated for thepurposes of simplicity as a single sheet, for example, of paper.However, the positive element 70 may comprise a support upon which atleast one liquid-permeable and dyeable layer is mounted.

The film unit also employs a negative sheet material or photosensitiveelement 72 comprising a support 74 of paper or film base material uponwhich there is mounted, in the order or sequence named, a layer 76comprising a profusion of minute capsules in substantial continguity,said capsules containing a dye such as a dye developer and having theouter surfaces thereof provided with a thin, light-reflecting coatingand a conventional photosensitive layer 78 of silver halide. Aspreviously noted, the use of a reflecting layer behind a silver halideemulsion layer but in front of a dye layer makes available otherwisewasted light for absorption by the emulsion while minimizing theabsorption by the dye of light needed for exposure.

As shown in FIG. 3 the photosensitive element 72 and the image-receivingelement 70, for the purpose of positive image formation, are adapted tobe placed in superposed relation and are arranged so that thephotosensitive layer or stratum 78 is next to the image-receivingelement 70.

Also, in the film unit of FIG. 3 a rupturable container 80, adapted tocarry an alkaline solution or liquid processing composition, is shownpositioned transversely of and adhered to the image-receiving element70. If desired, the container 80 may be adhered to the photosensitiveelement 72. Container 80 is of a length approximating the width of thefilm unit and is constructed to carry sufficient liquid to effectnegative image formation in an exposed image area of the photosensitivelayer 78 and positive image formation in the corresponding image area ofimage-receiving element 70. In use, the container 80 is adapted to bepositioned between the image-receiving element and the photosensitiveelement so that it will be adjacent the edges of the corresponding imageareas of these elements which are to be processed by the liquid contentsof the container. When the film unit is of the roll film type, aplurality of containers are employed, one for each corresponding pair ofsuccessive image areas in the photosensitive and image-receivingelements. The nature and construction of rupturable containers such asthat shown in FIG. 3 are well understood in the art; see, for example,U.S. Pat. Nos. 2,543,181 and 2,634,886.

Support 74 of the photosensitive element 72 may be transparent or opaqueand may comprise organic plastics, particularly those employed as filmbase materials, and may also comprise paper. Specific examples of thesupport materials comprise cellulose esters such as cellulose acetate,cellulose acetate butyrate and the like, certain nylon-type plastics andbaryta paper.

The photosensitive silver halide layer used herein is provided by silverhalide emulsions of the conventional character and is coated onto layer76 after the latter has dried. Emulsions of suitable sensitivity rangeare chosen to meet the particular requirements of use to which thephotosensitive element will be put. The silver halide is in allinstances used in a water- and alkali-permeable carrier material such asgelatin, although other water- and alkali-permeable materials known tothe art, may be substituted.

As heretofore mentioned, the image-receiving material of the positiveelement 70 includes any material dyeable by the dyes employed,preferably from alkaline liquid. The positive element 70 may, as shown,comprise a single sheet of permeable material or it may comprise, asshown in FIG. 4, a support which carries a layer or a stratum of apermeable image-receiving material. An example of such is imbibitionpaper or baryta paper or conventional film base material upon which apermeable stratum is coated. As a further example, the image- orprint-receiving element may comprise a paper support subcoated with asubstantially water-impremeable material such as a cellulose ester,i.e., cellulose acetate and the like, and having a stratum of apermeable and dyeable material coated over the subcoat.

Image-receiving materials of a dyeable nature, in addition to thosealready named, include gelatin; nylon, such as N-methoxymethylpolyhexamethylene adipamide; partially hydrolyzed polyvinyl acetate,such as that commercially available under the trade name of VinyliteMA-28-18 from Bakelite Division, Carbide and Carbon Chemicals Co.;polyvinyl alcohol with or without plasticizers; mixtures of polyvinylalcohol and N-polyvinylpyrrolidone, such as disclosed in the copendingapplication, Ser. No. 700,281, filed Dec. 3, 1957, now U.S. Pat. No.3,003,872; regenerated cellulose, sodium alignate, cellulose esters,such as methyl cellulose, or other cellulose derivatives such as sodiumcarboxymethyl cellulose or hydroxyethyl cellulose; mixtures of suchmaterials where they are compatible; and other materials of a similarnature such as are well known in the art. Where the image-receivingmaterial named tends to be dissolved by alkali, it may be used bysuitable cross-linking to preserve its film-forming ability. Theimage-receiving material may contain agents to mordant or otherwise fixthe dye transferred thereto.

It will be apparent that, by appropriate selection of theimage-receiving material from among the suitable known opaque andtransparent materials, it is possible to obtain either a color positivereflection print or a colored positive transparency.

The liquid processing composition employed in carrying out the inventioncomprises at least an aqueous alkaline liquid of sufficient alkalinityto permit the developer to perform its developing function and incertain instances may also contain a conventional black and whitedeveloper dissolved therein. While sodium hydroxide is in general thepreferred alkali used in the processing liquid, other alkaline materialmay be employed, for example potassium or lithium hydroxide, sodium orpotassium carbonate, and diethylamine. If the liquid processingcomposition is to be applied in a relatively thin, uniform layer, it mayalso include a viscosity-increasing compound constituting film-formingmaterial of the type which, when spread over a water-absorbent base,will form a relatively firm and stable film. A preferred film-formingmaterial is a high molecular weight polymer such as a polymeric,water-soluble ether inert to an alkali solution, as, for example, ahydroxyethyl cellulose or sodium carboxymethyl cellulose. Otherfilm-forming materials or thickening agents whose ability to increaseviscosity is substantially unaffected when left in solution for a longperiod of time may also be used.

In practice, the negative material or photosensitive element ispreferably exposed from the emulsion side. Following the exposure of thephotosensitive element 72 to a desired subject, the processing of theunit for transfer image formation proceeds by rupturing the containerand capsules and spreading the alkaline processing composition betweenthe photosensitive element 12 and the image-receiving element 70. Theprocessing liquid migrates or permeates into the separatealkali-permeable layers of the photosensitive element. During thepermeation into the capsular layer 76, unreacted dye contained in thislayer is dissolved in the processing liquid and is transported to thephotosensitive layer 78. As the process proceeds, the latent silverhalide image is developed, and as a result of the development, the dyein the exposed areas is immobilized. At least a portion of the mobiledye in the unexposed areas is imbibed to a superposed image-receivingelement 70 to create thereon a positive dye image.

Integral multilayer photosensitive elements or assemblages for use inmultilayer diffusion transfer processes are also applicable to theconcepts of the present invention. Two suitable assemblages areillustrated to FIGS. 4 and 5. Broadly, such multilayer assemblagescomprise at least two selectively sensitized photosensitive stratasuperposed on a single support and are processed, simultaneously andwithout separation, with a single common image-receiving element. Onesuitable arrangement comprises a support carrying a red-sensitive silverhalide emulsion stratum, a green-sensitive silver halide emulsionstratum and a blue-sensitive silver halide emulsion stratum, saidemulsions having associated therewith respectively a cyan dye, a magentadye and a yellow dye. After the foregoing strata are photoexposed, alayer of alkaline aqueous solution may be spread between the assemblageand image-receiving element. The various dyes, e.g., dye developers,react with exposed portions of the silver halide emulsions with whichthey are associated. Portions of the dye so reacted are immobilized andportions of the dye remaining unreacted migrate through the variouslayers of the assemblage and the layer of alkaline aqueous solution tothe print- or image-receiving element where they form a multicoloredprint.

In one embodiment, as shown in FIG. 4, the dyes, that is, the yellow dyedeveloper and magenta dye developer, are disposed in separateliquid-permeable layers behind the photosensitive silver halide stratumwith which they are associated. The cyan dye developer is encapsulatedwithin light-reflective capsules and a layer or coating of such capsulesis disposed behind the red-sensitive silver halide emulsion. In thisembodiment, the color-providing substances are thus located on the sideof the emulsion which is most distant from the photographed subject whenthe emulsion is exposed and also most distant from the image-receivingelement when in superposed relationship therewith.

FIG. 4 illustrates an assemblage comprising, in sequence, a support 92,a layer 94 comprising a profusion of minute capsules in substantialcontiguity, said capsules containing a cyan dye developer and having theouter surfaces thereof provided with a thin, light-reflecting coating, ared-sensitive silver halide emulsion layer 96, a magenta dye developerlayer 98, a green-sensitive silver halide emulsion layer 100, a yellowdye developer layer 102, and a blue-sensitive silver halide emulsionlayer 104. A processing composition 106 in the form of an aqueousalkaline solution is spread in a thin layer between photosensitiveelement 90 and image-receiving element 108 illustrated as a support 110having a dyeable layer 112 thereon.

FIG. 5 illustrates an assemblage 120 comprising, in sequence, a support122, a layer 124 comprising a profusion of minute capsules insubstantial contiguity, said capsules containing a cyan dye developerand having the outer surfaces thereof provided with a thin,light-reflecting coating, a red-sensitive silver halide emulsion 126, agreen-sensitive silver halide emulsion stratum 128 containing a magentadye developer, a yellow filter stratum 130, and a blue-sensitive silverhalide emulsion stratum 132 having dispersed therein a yellow dyedeveloper.

Yellow filter layer 130 is provided for attenuating light of wavelengths that must be prevented from affecting layers 124 and 128. Thus,filter layer 130 filters actinic light in the blue region of thespectrum. Auramine or colloidal silver are examples of suitable blueabsorbing filters. The silver may be incorporated in gelatin, whileauramine may be incorporated in cellulose acetate hydrogen phthalate.Interlayers or spacer layers (not shown), which, for example, arecomposed of gelatin, may be employed, for instance, between layers 126and 128 to confine the developing action of the dye developers to therespective emulsion layers with which they are originally associated.Such control or spacer layers may also be used in assemblages such asillustrated in FIG. 3. The components or elements shown in FIGS. 4 and 5are of compositions similar to those described in connection with FIG.3.

In practice, the photosensitive elements of FIGS. 4 and 5 are processedwhen an aqueous alkaline solution is supplied between the photosensitiveelement and the image-receiving element so as to permeate all the layersof the assemblage and solubilize the dye developer therein. As theprocess proceeds, the red-sensitive emulsion, green-sensitive emulsionand blue-sensitive emulsion are differentially developed by cyan dyedeveloper, magenta dye developer and yellow dye developer respectively,which, in consequence, become immobilized, more specificallyinsolubilized. On the other hand, the unexhausted or unreacted cyan dyedeveloper, magenta dye developer and yellow dye developer are free tomigrate in the solution to the image-receiving element where they form amulticolor print.

Another process for obtaining transfer images contemplates the use,behind the photosensitive layer, of a single layer comprising a profuserandom dispersion of at least two sets of capsules having the outersurfaces thereof provided with a thin light-reflecting coating, saidcapsules containinng therewithin suitable dye developers. One suitablephotographic assemblage or element 140 of this type is illustrated inFIG. 6 and comprises, in sequence, a support 142, a layer 144 comprisingin substantial contiguity a profusion of randomly dispersed capsuleshaving the outer surfaces thereof provided with a thin, light-reflectingcoating, one set or type of capsules containing a yellow dye developer,one type containing a magenta dye developer and one type containing acyan dye developer, and a suitably sensitized silver halide emulsionlayer 146. The processing of this photosensitive element is aspreviously described.

The color-providing substance is an organic compound and is a dye or adye intermediate such as a color coupler which is preferably soluble inalkali solutions. In a preferred embodiment, the color-providingsubstance is a complete dye and preferably a dye developer, i.e., acomplete dye which contains in the same molecule both the chromophoricsystem of a dye and also a silver halide developing function. By "asilver halide developing function" is meant a grouping adapted todevelop exposed silver halide. A preferred silver halide developingfunction is a hydroquinonyl group. Other suitable developing functionsinclude o-dihydroxyphenyl and o- and p- amino-substituted hydroxyphenylgroups. In general, the developing function includes a benzenoiddeveloping function. Preferred dye systems are azo and anthraquinone dyesystems.

The dye developers are preferably selected for their ability to providecolors that are useful in carrying out subtractive color photography,i.e., cyan, magenta and yellow. It should be noted that it is within thescope of this invention to use mixtures of dye developers to obtain adesired color, e.g., black. Thus, it is to be understood that theexpression "color" as used herein is intended to include the use of aplurality of colors to obtain black, as well as the use of a singleblack dye developer.

As examples of suitable dye developers, mention may be made of2-naphthylazohydroquinone,1-phenyl-3-methyl-4-[p-(2',5'-dihydroxyphenethyl)-phenylazo]-5-pyrazoloneand phenylazohydroquinone, for yellow; 2-hydroxynaphthylazohydroquinone,2-[p-(2',5'-dihydroxyphenethyl)-phenylazo]-4-methoxy-1-naphthol and1-amino-4-phenylazo-2-naphthol, for magenta;1,4-bis-(2',5'-dihydroxyanilino)-anthraquinone,1,4-bis-[β-(2',5'-dihydroxyphenyl)-ethylamino]-anthraquinone and1,4-bis-[β-(2',5'-dihydroxyphenyl)propylamino]-anthraquinone, for cyan.

Examples of representative dye developers are given in the previouslymentioned application of Howard G. Rogers, Ser. No. 748,421, now U.S.Pat. No. 2,983,606.

It is also contemplated to use dye developers initially in the form of ahydrolyzable derivative particularly in the form of a hydrolyzable esteror salt and wherein said hydrolyzable derivative is subjected tohydrolysis conditions during processing. Such hydrolyzable dyedevelopers are dye developers containing a grouping removable byhydrolysis, which group renders the dye developer substantially lessmobile and/or less soluble until such grouping is removed by alkalinehydrolysis.

A more detailed discussion relating to hydrolyzable dye developers isset forth in the copending application of Land et al, Ser. No. 669,542,filed July 2, 1957, now abandoned.

In addition to dye developers of the above-mentioned types, it is alsocontemplated to utilize dye developers with temporarily shiftedabsorption characteristics such as set forth in the copendingapplication of Howard G. Rogers, Ser. No. 789,080, filed Jan. 26, 1959and now abandoned.

The expression "temporarily shifted", as used above, is intended tosignify color-providing substances, the spectral absorption bands ofwhich are located at wave lengths which exhibit less absorption, withrespect to the ultimate image dye, within the sensitivity range ofassociated photosensitive silver halide for at least the time intervalnecessary to accomplish photoexposure of the respective photosensitivesilver halide. Such color-providing substances are subjected tononreversible shift of the color-providing substances' absorptioncharacteristics subsequent to photoexposure.

In addition to dye developers as described above, other color-providingsubstances may be employed to create colored positive images. Asexamples of other color-providing substances, mention may be made of thedyes of the type described in U.S. Pat. 2,774,668 and the other patentsand copending applications heretofore referred to. Dyes which areparticularly suited for reacting with an oxidation product of adeveloper are found in those having an open position on a ring, whichposition is para to a hydroxyl or an amino group, or those dyes having areactive methylene group. Many suitable dyes coming within theclassification are found among the azo, pyrazolone and triphenyl methanedyes, specific examples of which comprise the following water- andalkali-soluble dyes such as Fast Crimson 6Bl (CI 57) for magenta; FastWool Yellow (CI 636) for yellow; Alphazurine 2G (CI 712) and PontacylGreen SX Extra (CI 737) for cyan; and Polychrome Blue-Black (CI 201) andRayon Black GSP (commercially available from E. I. duPont) for black; aswell as the water-insoluble but alkali-soluble dyes such as1,5-dihydroxynaphthalene-4-azobenzene for magenta and Benzene AzoResorcinol (CI 23) for yellow. When utilizing dyes of the above type,nondiffusing or substantially immobile silver halide developers arepreferably employed so as to keep the developer out of theimage-receiving element. Dyes which are rendered nondiffusible by theimagewise exhaustion of alkali, as disclosed in the copendingapplication of Edwin H. Land, Ser. No. 640,821, filed Feb. 18, 1957, nowabandoned, are also useful in practicing this invention. The inventiveconcepts herein set forth are also adaptable for the formation ofcolored images in conjunction with the photographic products and screenprocesses described and claimed in U.S. Pat. No. 2,968,554, issued Jan.17, 1961 to Edwin H. Land. In this patent, at least two selectivelysensitized silver halide emulsions are arranged in the form of a screenand the encapsulated color-providing substances, as in multilayerelements, are placed behind the photosensitive emulsion with which theyare associated.

It should be noted that it is within the scope of this invention toutilize in multicolor diffusion transfer processes, one or more of theabove described color-providing substances in a single photosensitiveelement. For example, in certain instances it may be desirable to employdye developers with temporarily shifted characteristics in associationwith blue-sensitive and green-sensitive capsules, together with anotherclass of dye developers or color-providing substance.

In a preferred embodiment, an auxiliary or accelerating developing agentis used in combination with dye developer. Thus, the liquid processingcomposition may contain an auxiliary or accelerating developing agent. Apreferred accelerating developing agent is a 3-pyrazolidone developingagent and preferably 1-phenyl-3-pyrazolidone which is available underthe trade name "Phenidone" from Ilford Limited. It is also contemplatedto employ a plurality of auxiliary or accelerating developing agents,such as a 3-pyrazolidone developing agent and a benzenoid developingagent, as disclosed and claimed in the copending application of HowardG. Rogers and Harriet W. Lutes, Ser. No. 654,781, filed April 24, 1957,now U.S. Pat. No. 3,939,869. As examples of suitable combinations ofauxiliary developing agents, mention may be made of1-phenyl-3-pyrazolidone in combination with p-benzylaminophenol and of1-phenyl-3-pyrazolidone in combination with 2,5-bis-ethyleniminohydroquinone. Such auxiliary developing agents may be employed in theliquid processing composition or they may be initially incorporated, atleast in part, in the silver halide sensitized capsule containing thedye developers.

As stated above, it has heretofore been proposed to form color images bya diffusion-transfer process utilizing color-providing substances suchas, for example, dye developers. In processes of this type, aphotosensitive element containing a color-providing substance and asilver halide emulsion is exposed and wetted by a liquid processingcomposition, for example, by immersing, coating, spraying, flowing,etc., in the dark; and the exposed photosensitive element is superposedprior to, during or after wetting on a sheetlike support element whichmay be utilized as an image-receiving element. In a preferredembodiment, the liquid processing composition is applied to thephotosensitive element in a substantially uniform layer as thephotosensitive element is brought into superposed relationship with animage-receiving element. The liquid processing composition permeates theemulsion to initiate development of the latent image contained therein.The color-providing substance is immobilized or precipitated in exposedareas as a consequence of the development of the latent image. Inunexposed and partially exposed areas of the emulsion, thecolor-providing substance is unreacted and diffusible and thus providesan imagewise distribution of diffusible, unreacted color-providingsubstance dissolved in the liquid processing composition as a functionof the point-to-point degree of exposure of the silver halide emulsion.At least part of this imagewise distribution of unreacted color-formingsubstance is transferred, by imbibition, to a superposed image-receivinglayer or element. Under certain conditions, the layer of the liquidprocessing composition may be utilized as the image-receiving layer.There is then produced on or in the image-receiving element a reversedor positive color image of the developed image. The image-receivingelement may contain agents adapted to mordant or otherwise fix thepositive color image. If the color of the transferred color-providingsubstance is affected by changes in the pH of the image-receivingelement, this pH may be adjusted in accordance with well-knowntechniques to provide a pH affording the desired color. The desiredpositive image is revealed by stripping the image-receiving element fromthe photosensitive element at the end of a suitable imbibition period.

In prior diffusion-transfer processes, the photosensitive elementscomprised at least one silver halide emulsion layer and at least onecolor-providing substance which could be present in the emulsion layeror in a layer on or behind the emulsion. The layers employed in suchelements generally consist of a continuous gelled colloid film in whichthe silver halide and/or color-providing substance is dispersed, thatis, the dispersed material constitutes discrete inclusions or adiscontinuous phase within the continuous colloid phase.

In instances where the color-providing substances possess a color,undesirable light absorption by the color-providing substance may resultin reducing the sensitivity of silver halide emulsions. Utilizing one ormore color-providing substances in layers behind photosensitive silverhalide emulsion layers adds to the bulk or thickness of thephotosensitive element. This is particularly so when multicolor printsare to be obtained from a single photosensitive element.

It has been found that photosensitive elements with a minimum number oflayers may be obtained, in addition to substantially reducing oreliminating the disadvantage of desensitization of the silver halideemulsion by colored color-providing substance associated therewith, byhaving said color-providing substance or substances encapsulated in acoating of an alkali-permeable film-forming polymeric material such as,for example, gelatin and having the outermost wall of the capsulescoated with silver halide. Thus, there may be provided a photosensitiveelement including a support and at least one layer or coating thereoncomprising in substantial contiguity a profuse number of minute capsulesof alkali-permeable film-forming polymeric material containingtherewithin a color-providing substance, the outermost walls of thecapsules being coated with silver halide. The silver halide coating maybe appropriately sensitized. A capsular layer may comprise insubstantial contiguity single or individual capsules which all containthe same color-providing substance, or it may comprise individualcapsules some of which contain one color-providing substance and othersof which contain other color-providing substances. For example, thecapsular layer may comprise capsules holding only a magenta dyedeveloper; or the layer may comprise a mixture of capsules some of whichhold a magenta dye developer, others of which hold a cyan dye developerand still others of which hold a yellow dye developer.

A capsular layer may also comprise a mixture of individual capsules someof which contain color-providing substance and others of which contain areagent or reactive material useful in the formation of the desiredimages and which reagent or reactive material is preferably maintainedor separated from contact with the color-providing substance untilneeded.

The color-providing substance per se, may be contained within thecapsules and solubilized by an alkaline processing composition, or itmay be dissolved or suspended in a suitable liquid medium or vehiclewithin the capsule. The liquid medium or vehicle employed within thecapsule should not adversely affect the encapsulating material, norshould it interfere in the formation of the colored print. When theencapsulating material is of a hydrophilic nature, the medium within thecapsule, if employed, is preferably of water-immiscible liquid. Suitablewater-immiscible liquid mediums which may be employed are vegetable oilssuch as cottonseed oil, coconut oil, and castor oil; animal oils such assperm oil and lard oil; petroleum fractions such as paraffin oil;synthetic oils such as methyl salicylate and the like. When theencapsulating material is of a hydrophobic nature, the medium, ifemployed, carrying the color-providing substance may comprise water oran organic material. When an aqueous medium is utilized, there may alsobe employed therewith a suitable water-miscible organic liquid which isdesirable to have incorporated within the capsules.

In order to render the capsular material produced by the heretoforedescribed techniques photosensitive, the outermost wall of theencapsulating material is impregnated or coated with appropriatelysensitized silver halide. This may be accomplished in many ways. Forexample, the silver halide may be suspended in a suitable volatilevehicle and the capsules treated therewith. Upon evaporation or removalof the vehicle, the silver halide will be imbedded in and around theoutermost capsule wall. The silver halide coating may then be suitablysensitized. It is also possible to disperse silver halide in a suitablesolution of a binder and coat the outermost capsule walls therewith, thebinder such as, for example, gelatin, in this case being used to aid thesilver halide is adhering to the capsule walls. Additionally, it ispossible to chemically plate silver onto or into the outermost capsulewalls and then subject the silver coated capsules to the desired halogenvapors so as to form a silver halide coating, which is thereaftersuitably sensitized. Alternatively the capsules may be coated withsilver by well-known vapor deposition techniques such as, for example,vacuum deposition, and thereafter subjected or treated with the desiredhalogen vapors to form a silver halide coating around the outermostcapsule walls. The appropriate sensitization of the silver halidecoating with a photosensitizing agent such as a silver halide opticalsensitizing agent or a hypersensitizing agent may be accomplished byvacuum deposition techniques or other known methods.

The photosensitized capsules may be coated on a suitable support, e.g.,paper, or layer, e.g., previously coated capsular layer, by techniqueswhich are well known in the art, e.g., by rollers, spray, brushes or anyof the commonly used methods, and then allowed to dry. The capsules whendry are adherent to the support or layer overcoated therewith and toeach other in a film.

As mentioned previously, the capsular layer of a photosensitive elementmay comprise a mixture of individual capsules some of which arephotosensitized with silver halide and which contain a color-providingsubstance and others of which are not photosensitized and which containa reagent or reactive material useful in the formation of the desiredimages and which reagent or reactive material is preferably maintainedor separated from contact with the color-providing substance. Capsulesof the latter type, i.e., non-photosensitive, may comprise, for example,gelatin capsules containing an auxiliary or accelerating developingagent such as 1-phenyl-3-pyrazolidone. These non-photosensitizedcapsules may be produced by the methods described above except that thesilver halide coating is omitted although such capsules may have a thincontinuous coating such as of aluminum to render the capsules moreimpermeable.

Several embodiments wherein the silver halide coated capsules may beutilized are illustrated in the accompanying drawings. References to dyedevelopers in the description of these embodiments is intended to beillustrative only. While the preferred color-providing substances aredye developers and the several embodiments are illustrated by the use ofdry developers, it is to be understood that other types ofcolor-providing substances may be employed.

One embodiment of a photographic film unit or assembly useful incarrying out a one-step photographic process for the formation of animage of an individual color is illustrated in FIG. 7 as comprising aphotosensitive element 150, a print-receiving element 156 and arupturable container 162 for holding a liquid processing fluid orcomposition.

The photosensitive element 150 comprises a conventional paper or plasticfilm base or support 152 and a photosensitive layer 154 comprising, insubstantial contiquity, a profusion of minute capsules ofalkali-permeable film-forming polymeric material coated with silverhalide appropriately sensitized, said capsules containing acolor-providing substance such as a dye developer. As shown in theparticular embodiment depicted in FIG. 7, the photosensitive element 150is shown in a spread-apart relationship with an image-receiving element156 having mounted thereon a rupturable container 162 holding aprocessing composition. The image-receiving element 156 comprises adyeable material and may comprise a single image-receiving layer or, asshown, an image-receiving layer 158 carried by a support 160. Afterexposure, the image-receiving element 156 is brought into superposedrelationship with the photosensitive element 150, and the rupturablecontainer 162 is ruptured by application of suitable pressure, e.g., byadvancing between a pair of rollers (not shown); and a layer of theliquid processing composition is spread between the superposed elements.The processing composition permeates into the capsular photosensitizedlayer 154 to initiate development of the latent image in the exposedsilver halide regions. In exposed silver halide areas, the dyedeveloper, for example, carried by the capsules, will be reacted andbecome immobilized. In unexposed areas, the dey developer will be mobileand will diffuse to the superposed image-receiving element 156. After asuitable imbibition period, the photosensitive element 150 and theimage-receiving element 156 are separated to reveal the positive coloredimage.

Multicolor images may be obtained using dye developers indiffusion-transfer reversal processes by several techniques. One suchprocess for obtaining multicolor transfer images utilizing dyedevelopers employs an integral multilayer photosensitive element whereinat least two selectively sensitized photosensitive layers are superposedon a single support and are processed simultaneously and withoutseparation, with a single common image-receiving layer. A suitablearrangement of this type comprises a support carrying a red-sensitivesilver halide layer, a green-sensitive silver halide layer and ablue-sensitive silver halide layer, said layers having associatedtherewith, respectively, a cyan dye developer, a magenta dye developerand a yellow dye developer. Each dye developer is encapsulated withinminute capsules of alkali-permeable polymeric materials, the outermostwalls of said capsules being suitably sensitized with silver halide.

A multilayer photosensitive element of the type just described isillustrated in FIG. 8 of the accompanying drawings and is depictedduring processing. A exposed multilayer photosensitive element 170comprises a support 172; a photosensitive layer 174 comprising insubstantial contiguity, a profusion of red-sensitized silver halideminute capsules of alkali-permeable polymeric material, said capsulescontaining a cyan dye developer; a photosensitive layer 176 comprisingin substantial contiguity, a profusion of green-sensitized silver halideminute capsules of alkali-permeable polymeric material, said capsulescontaining a magenta dye developer; and a photosensitive layer 178comprising in substantial contiguity, a profusion of blue-sensitizedsilver halide minute capsules of alkali-permeable polymeric material,said capsules containing a yellow dye developer. Each photosensitivelayer may be separated from each other by suitable interlayers (notshown), for example, by a layer of gelatin and/or polyvinyl alcohol. Incertain instances it may be desirable to incorporate a yellow filter infront of the green-sensitive layer, and such yellow filter may beincorporated in an interlayer. A yellow filter layer may be preparedusing a pigment comprising a suspension of a benzidine yellow, such asthat commercially available under the name of "Padding Yellow GL" fromTextile Colors Division, Interchemical Corporation, Hawthorne, N. J.However, where desirable, a yellow dye developer of the appropriatespectral characteristics and present in a state capable of functioningas a yellow filter may be employed. In such instances a separate yellowfilter may be omitted.

Referring again to FIG. 8, a multilayer photosensitive element 170 isshown in processing relationship with an image-receiving element 180 anda layer 186 of a processing composition. The image-receiving element 180comprises a support 182 and an image-receiving layer 184.

As noted in connection with FIG. 7, the liquid processing composition iseffective to initiate development of the latent image in the respectiveexposed photosensitive layers. After a suitable imbibition period,during which at least a portion of the dye developer associated withunexposed areas of each of the photosensitive layers is transferred tothe superposed image-receiving element 180, the latter element may beseparated to reveal the positive multicolor image.

Although the structure of the integral, multilayer photosensitiveelement has been illustrated as having photosensitive layers from top tobottom sensitized to blue, green and red portions of the spectrum,respectively, it is to be understood that the order of these layers mayvary in accordance with well-known practices in the art.

The expression "integral multilayer photosensitive element" as usedherein is intended to include photosensitive elements comprising atleast two separate, superposed layers of photosensitive material, eachlayer being selectively sensitized to an appropriate portion of thespectrum, at least the inner layer or layers having associated therewithappropriate color-providing substances. The integral multilayerphotosensitive element is intended to be processed without separation ofthe layers. The imagewise distribution of diffusible color-formingsubstances present in each layer as a result of the development oflatent images therein is transferred to a single, common image-receivingelement to provide the desired multicolor image.

As will be demonstrated hereinafter, the term "layer" is intended toinclude a stratum comprising a mixture of at least two differentlyphotosensitized capsular materials. Thus, such a stratum may comprise amixture of two or more sets or types of minute capsules ofalkali-permeable polymeric material, each set being suitably sensitizedwith silver halide and encasing or containing therewithin an appropriatecolor-providing substance. The term "layer" also contemplates a stratumcomprising at least two sets of selectively sensitized minutephotosensitized capsular materials arranged in the form of aphotosensitive screen.

Another process for obtaining multicolor transfer images utilizing dyedevelopers contemplates the use of a single photosensitive layercomprising a profuse random dispersion of at least two sets ofselectively sensitized minute capsules of alkali-permeable polymericmaterial, said capsules containing therewithin a suitable dye developer.One suitable arrangement of this type comprises a support carrying as asingle layer red-sensitized minute capsules containing a cyan dyedeveloper, green-sensitized minute capsules containing a magenta dyedeveloper and blue-sensitized minute capsules containing a yellow dyedeveloper, said capsules being profusely and randomly dispersed.

A photosensitive element of the type just described is illustrated inFIG. 9 of the accompanying drawings and is depicted during processing.An exposed photosensitive element 190 comprises a support 192 and aphotosensitive layer 194 comprising in substantial contiguity aprofusion of randomly dispersed red-sensitized silver halide minutecapsules of alkali-permeable polymeric material containing a cyan dyedeveloper, green-sensitized silver halide minute capsules ofalkali-permeable polymeric material containing a magenta dye developerand blue-sensitized silver halide minute capsules of alkali-permeablepolymeric material containing a yellow dye developer. As illustrated,photosensitive element 190 is in processing relationship with animage-receiving element 196 and a layer 202 of a processing composition.The image-receiving element 196 comprises a support 198 and animage-receiving layer 200. The processing of exposed photosensitiveelement 190 is as previously described.

Another technique for obtaining multicolor transfer images utilizing dyedevelopers contemplates the use of a photosensitive layer comprising atleast one sets of selectively sensitized minute capsules arranged in theform of a photosensitive screen. In such an embodiment each of theminute capsules has contained therewithin a suitable dye developer. Ingeneral, a suitable photosensitive screen comprises red-sensitizedminute capsules containing a cyan dye developer, green-sensitized minutecapsules containing a magenta dye developer, and blue-sensitized minutecapsules containing a yellow dye developer arranged in side-by-siderelationship in a screen pattern.

A photosensitive color screen element of the type just described isillustrated in FIG. 10 of the accompanying drawings wherein thephotosensitive element 210 comprises, respectively, a support 212 and aphotosensitive color screen layer 214 which comprises selectivelyexposable portions, that is, portions which comprise, respectively,red-, green- and blue-sensitized silver halide minute capsulescontaining therewithin, respectively, cyan, magenta and yellow dyedevelopers, preferably substantially uniformly distributed over thesupport such that a contiguous layer arrangement of individualselectively exposable portions have their respective exposure facesarranged in a side-by-side screen pattern relationship and forming theexposure surface of photosensitive element 210. As shown, photosensitiveelement 210 is in processing relationship with an image-receivingelement 216 and a processing composition 222. The image-receivingelement 216 comprises a support 218 and an image-receiving layer 220.The processing of exposed photosensitive element 210 is as previouslydescribed.

Moreover, the techniques of this invention may be utilized in two-colorprocesses as well as the three-color photographic processes illustratedin FIGS. 8, 9 and 10. Thus, for example, although photosensitiveelements for three-color processes have been shown, photosensitiveelements for use in two-color processes may be constructed and processedin a similar manner. For example, an integral multilayer photographicelement suitable for two-color processes may have one layer of minutecapsules sensitized to the blue and green portions of the spectrum, saidcapsules containing an orange dye developer and another layer of minutecapsules sensitized to the orange and red portions of the spectrum, saidcapsules containing a cyan dye developer. Obviously, the sensitivitiesof the layers or sets of minute capsules may be selected in accordancewith well-known photographic principle.

While the above assemblages have been described in connection with colorprocesses involving the application of but one processing solution, itshould be understood that they may also be employed in processesinvolving the application of several processing compositions, as, forexample, the multiple step processes set forth in the copending U.S.application of Edwin H. Land, Ser. No. 663,732, filed June 5, 1957, nowabandoned and of Edwin H. Land et al, Ser. No. 665,807, now abandonedfiled June 14, 1957.

Throughout the specification and appended claims, the expression"positive image" has been used. This expression should not beinterpreted in a restrictive sense since it is used primarily forpurposes of illustration, in that it defines the image produced on theimage-carrying layer as being reversed, in the positive-negative sense,with respect to the image in the photosensitive element. As an exampleof an alternative meaning for "positive image", assume that thephotosensitive element is exposed to actinic light through a negativetransparency. In this case, the latent image in the photosensitiveelement will be a positive and the image produced on the image-carryinglayer will be a negative. The expression "positive image" is intended tocover such an image produced on the image-carrying layer.

Since certain changes may be made in the above product and processwithout departing from the scope of the invention herein involved, it isintended that all matter contained in the above description or shown inthe accompanying drawings shall be interpreted as illustrative and notin a limiting sense.

What is claimed is:
 1. Microscopic capsules consisting essentially of asubstantially continuous film-forming polymeric layer surrounding anucleus comprising a color-providing substance, said polymeric layerhaving a substantially continuous metallic layer thereover. 2.Microscopic capsules as defined in claim 1 wherein the color-providingsubstance is a dye.
 3. Microscopic capsules as defined in claim 2wherein said dye is a dye developer.